Rudolf e



R. E. HELLMUND.

SYSTEM OF CONTROL.

APPLIICATIGN HLED OCT. as, 1918.

1358,'?3?=, I Patented Nov. 16,1920.

. I 770 e Fig/ Hy WETNESSES: INVENTOR Mam W HMO/f 5. Hel/mund UNITED STATES PATENT OFFICE.

RUDOLF E. HELLMUND, OF'SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

SYSTEM OF CONTROL.

1,358,737, Specification of Letters Patent. Patented Nov, 16 1920.

Original application filed October 24,

To all whom it may concern I Be it known that I, RUooLFE. HELLMUND, a citizen of the GermanEmpire,and a resident of Swissvale, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Control, of which the following is a'specification; this a plication being a division of application erial No. 127,381, filed October-24, 1916, patented October 28, 1919, No. 1,320,053.

My invention relates to systems of control for dynamo-electric machines, and it has special relation to the regenerative control of electricmotors that are adapted for use in propelling electric railway vehicles, and the like.

One object of my invention is to provide simple, durable, and reliable means for effecting regenerative operation of the momentum-driven armatures of motors of the above-indicated character, whereby a cer tain proportion of the energy absorbed during the propelling period is returned to the supply circuit, to reduce operatin expenses, and wherebyvarious other well-known operating advantages are secured.

Another object of my invention is to pro vide a system of regenerative control which shall embody means for automatically compensating for the unavoidable voltage fluctuations in the supply-circuit voltage,whereby a substantially constant regenerated current is maintained during such fluctuations.

More specifically stated, an object of my invention is to provide a motor-generator set or dynamotor of relatively small capacity for variably energizing the main series field magnet winding of the propelling motor or motors during regenerative operation. The set may be driven either from a predetermined portion of the regenerative circuit or from a suitable external source of energy.

Viewed from another angle, it is an object of my invention to provide a regenerative system employing substantially constant main-field winding excitation that is essentially independent of the supply-circuit volt age, but is dependent upon the regenerated current for purposes to be set'forth.

The various novel circuit arrangements Divided and this application filed October and connections employed in myinvention may best be understood by reference to the accompanying drawings,in which Figures 1 to 3, inclusive, are diagrammatic views of the main circuit connections of various control systems embodying my invention; and Fig. 4 is a curve chart serving to illustrate certain operating characteristics of one of my auxiliary machines.

Like reference characters designate like parts in all of the figures.

The systems to be set forth are relatively simple in arrangement by reason of the fact that either a motor-generator or a battery alone is used in connection with the mainfield-Winding excitation, whereas, in many prior systems, both are utilized. Moreover, in such prior systems wherein the mainfield-Winding excitation is entirely independent of. the trolley voltage, the unavoidable fluctuations of trolley voltage may, at times, produce undesirable effects, particularly in the case of a sudden interruption of supply-circuit voltage, when relatively heavy currents may occur for an instant.

()n the other hand, in systems of the class wherein the main field-winding-excitation voltage is dependent upon the supply-circuit voltage, so thatsuch excitation varies with the supply-circuit voltage and thus, the above-mentioned excessive currents cannot occur, the system is inherently adapted to produce undesirably high regenerated volt tage upon a sudden decrease or interruption of supply-circuit voltage, since the inherent tendency, in many systems, is-to maintain a main-field-winding excitation that is sufficient to provide a main armature or regenerated voltage that is higher than the normal supply-circuit voltage by a predetermined amount. Particularly, in systems that employ a motor-generator set or the like that is driven from the regenerated voltage, the cycle of operation is such as to successively increase the regenerated voltage that is supplied to the motor-generator set-and thus increase the mainfield-winding excitation and, therefore, the main-armature or regenerated voltage. Under such conditions, a dangerously high regenerated voltage is liable to be attained in the course of a second or so, thereby leading to f flashover ,troubles and the like in the main motors or in'the driving motor otthe auxiliary motor-generator set.

A compromise system which embodies the good features of both of the above-mentioned classes of systems may be obtained by making the main-field-winding excitation normally essentially independent of the supply-circuit voltage, and by preventing excessive regenerated currents, either by making such excitation dependent upon the regenerated current in a suitable manner or by makin such excitation only temporarily dependent upon the supply-circuit voltage, until relays or other control devices have been givcntime to operate and either interrupt the circuit connections or change them to correspond to the new values of supply circuit voltage, This comoromise feature is embodied in the following systems.

Referring to Fig. 1 of the drawings, the system here shown comprises a supply circuit that includes a supply conductor marked Trolley and a return'circuit conductor marked Ground; trio machine such as a direct-current railway motor, for example, ha *ing'an armature A1 and a series-type field winding F1; and an auxiliary 'motor-generator set comprisin a motor M that is supplied with prope ling energy from the supply circuit'and a generator or exciter Gr, that is suitably mechanically connected to the motor M, as by a shaft S.

The auxiliary driving motor is provided with a shunt field winding 1, which may be varied by a resistor 2, while the auxiliary generator has a shunt field winding 4;. An inductive device 106 is connected in series relation with the main armature A1, across the supply circuit, and the auxiliary generator is connected through the device 106 across the main field winding F1. The desired negative compounding effect is thereby obtained, as about to be set forth. As indicated by the solid and the dotted arrows, respectively, the main-armature or. regenerated current traverses the inductive device 106 in the same directionas the mainfield-winding or exciting current Consequently, an incipient increase of regenerated current correspondingly increases the voltage drop across the inductive device 106, thus proportionately reducingthe voltage available for delivery to the main fieldwinding F1 from the auxiliary generating armature, and likewise decreasing the mainmachine excitation to cause the regenerated current to subside to a normal value. llhe converse action takes place in the event of an incipient decrease of main-armature current. The effect just described is a temporary one, by reason of the well-known inductive kick that occurs upon sudden changes of current conditions.

a dynamo-elec- By designing the motor-generator set so that the auxiliary motor has a relatively unsaturated iield-magnetic circuit, while the auxiliary generator has a relatively highly saturated field-magnetic circuit, as. more fully set forth below, a substantially constant volta e is delivered by the generator armature I under conditions of supplycircuit voltage variation, but the main-field- Kvinding excitation is temporarily influenced curve of the field-winding magnetic circuit.

As is well-known, main dynamo-electric machines and, in particular, auxiliary driving motors, of the class in question normally have their field-windin ma netic circuits relatively highly saturated; that is to say, the machines operate with a normal'degree of saturation that corresponds to the point Y in the curve which is located above the bend or knee thereof. In the present instance, however, the auxiliary driving motor is adapted to operate with a degreeof fieldwinding-magnetic-circuit saturation that is relatively low and corresponds to the point X of the curve, which is located upon the straight-line portion thereof below the bend or knee. Thus, the auxiliary driving motor inherently possesses relatively great stability and is economical in operation, as will be appreciated by those skilled in the art.

On the contrary, the magnetic circuit for the field winding of the auxiliary generating armature G is preferably saturated to a relatively high degree, so that, with the practically constant-speed conditions under which the motor-generator set operates, the exciter voltage tends to remain substantially constant.

In Fig. 2, a similar result is obtained by substituting the constantvoltage battery B for the auxiliary motor-generator set that is shown in Fig. 1, as will belunderstood. The variable field-winding-circuit resistor 101 may be utilized, if desired, in both of the systems that are illustrated in Fig. 1 and in Fig. 2 for the above-mentioned purpose of compensating i orthe decrease of vehicle speed.

Fig. 3 shows a system in which certain desirable operating features of the system that is shown in Fig. l are combined with others; that is to say, the auxiliary field winding 103 for the generator armature G is utilized to provide a hastening action upon the main-field-winoing excitation changes in the case of supply-circuit-voltage fluctuations, as explained below, and, in

addition, the inductive device 106 is connected in the common portion of the main armature and main-field-winding' circuits to inherently produce the desired temporary negative compounding effect, as previously explained. The above-mentioned hastening action is effected by the location of the auxiliary field winding 103, whereby the desired counteracting of variations of the mainfield-winding excitation is made temporarily dependent upon changes of the supplycircuit voltage. In general, the design of parts of the motor-generator set corresponds to that set forth in connection with Fig. 13 and to the curve of Fig. 14 in the aboveidentified application of which this is a di vision, such curve corresponding to the present Fig. 4. In addition, in case of an. in crease or upward fluctuation of the supplycircuit voltage, the current traversing the circuit that includes the auxiliary driving armature winding M and the field winding 103 for the generator armature G is correspondingly increased to thus augment the delivered voltage of the armature G and finally, therefore, to increase the effective flux that is produced by the total field winding F1. In this way, the regenerated voltage of the main armature A1 is raised a predetermined amount in a relatively short space of time to thus tend to maintain a substantially constant difference between the main-armature voltage and the supply-circuit voltage, whereby a practically constant regenerated current is supplied. The converse action occurs upon a decrease of sup ply circuit voltage, as will be uinlerstood. The motor-generator set is of the special type hereinbefore set forth in connection with the curve of Fig. 4; that is, the auxiliary motor has a relatively unsaturated field-magnetic circuit, whereas, the corresponding circuit of the auxiliary generator is relatively highly saturated. o compensate for the decrease of vehicle speed, the variable field-winding-circuit resistor 101 may be gradually excluded from circuit, or other previously-described methods may be employed.

I do not wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of my invention. I desire, therefore, that onl such limitations shall be imposed as are in icated in the appended claims.

I claim as my invention:

1. In a system of regenerative control. the combination with a supply circuit and a dynamo-electric machine having .an armature and a field winding, of an auxiliary motor-generator driven from said supply circuit and adapted to deliver a substantially constant voltage, which is substantially independent of the supply-circuit voltage,

for exciting-said field winding, and means only temporarily influenced by regenerated-current variations to change the field excitation. I

2. In a system of regenerative control, the combination with asupply circuit and a main dyna-nmclectricmachine having an annature, and a field winding, of an auxiliary motor-generator having one of its armatures driven from the supply circuit and the other connected to separately excite said field winding, the magnetic circuit of the auxiliary driving motor being relatively unsaturated and a field winding for the exciting armature being connected in series relation with the auxiliary driving armature 3. In a system of regenerative control, the combination with a supply circuit and a main dynamo-electric machine having an armature and a field winding, of an auxiliary motor-generator having one of its arinatures driven from the supply circuit and the other connected to separately excite said field winding, the magnetic circuit of the auxiliary driving motor being relatively unsaturated and the magnetic circuit of the auxiliary exciting armature being relatively highly saturated, and a field winding for the exciting armature being connected in series relation with the auxiliary driving armature.

4. In a system of regenerative control, the combination with a supply circuit and a main (lynamdelectric machine having an armature and a field Winding, of an inductive device connected in series circuit relation with. the main armature, and an aux iliary motor-generator having one of its filI'IIlEli'llI'BS driven from the supply circuit and the other connected to excite said field winding through said inductive device, the auxiliary generator having a field winding connected in series relation with the auxiliary motor armature.

In a system of regenerative control, the combination with a supply circuit and a main dynamo-electric machine having an armature and a field winding, of an inductive device connected in series circuit relation with the main armature, and an auxiliary motongenerator having one of its armatures driven from the supply circuit and the other connected to excite said field winding through said inductive device, the ma netic circuit of the auxiliary driving motor eing relatively unsaturated, and the magnetic circuit of the auxiliary generator being rela,

tively highly saturated, and the auxiliary generator having a field winding connected in series relation with the auxiliary motor armature.

6. In a system of regenerative control, the combination with a supply circuit and a main dynamo-electric machine having an rli L armature anda field Winding, of an inductive device connected in series circuit rela tion With the inainermature, an auxiliary motor-generator having one of its armatures driven from the supply circuit and the other connected to excite said field Winding through said inductive device, the auxiliary generator having a field Winding connected in series relation With the auxiliary motor armature, and a shunt field Winding for said 10 motor armature.

In testimony whereof, I have hereunto subscribed my name this 30th day of Sept, 1918.

RUDOLF E. HELLMUND. 

